The embodiments herein relate to the use of volatile surfactants to increase the recovery of gas or oil from subterranean formation, including during enhanced oil recovery operations.
Subterranean wells (e.g., hydrocarbon producing wells, gas producing wells, and the like) are often stimulated by hydraulic fracturing treatments. In traditional hydraulic fracturing treatments, a treatment fluid, which may also function simultaneously or subsequently as a carrier fluid, is pumped into a portion of a subterranean formation (which may also be referred to herein simply as a “formation”) at a rate and pressure sufficient to break down the formation and create one or more fractures therein. Typically, particulate solids, such as graded sand, are suspended in a portion of the treatment fluid and then deposited into the fractures. The particulate solids, known as “proppant particulates” (which may also be referred to herein as “proppant” or “propping particulates”) serve to prevent the fractures from fully closing once the hydraulic pressure is removed. By keeping the fractures from fully closing, the proppant particulates aid in forming conductive paths through which fluids produced from the formation flow, referred to as a “proppant pack.” The degree of success of a stimulation operation depends, at least in part, upon the porosity of the proppant pack to permit the flow of fluids through the interconnected interstitial spaces between abutting proppant particulates.
In some cases, subterranean treatment operations (e.g., hydraulic fracturing, and the like) may be supplemented with enhanced oil recovery (EOR) techniques. EOR techniques are used increase recovery of production fluids (e.g., hydrocarbons) by restoring formation pressure and improving fluid flow in the formation and typically involve injection of a substance that is not naturally occurring in a hydrocarbon-bearing formation. One EOR technique involves introducing a flooding composition into the subterranean formation in order to pressurize the formation and drive hydrocarbons toward one or more production wells. Such flooding compositions may be a gas (in gas injection operations) or a combination of a gas and water. When the flooding composition is a combination of gas and water, the flooding composition may be injected into the formation by alternating the injection of the gas and the water (referred to as a water alternating gas (“WAG”) technique) or by simultaneously injecting the gas and the water (referred to as a simultaneous water and gas injection (“SWAG”) technique).
WAG and SWAG techniques may increase hydrocarbon recovery as compared to standard gas injection by an additional 5-20% because the gas and water operate synergistically to enhance oil recovery. The gas is absorbed by the hydrocarbons in the formation, thereby reducing the viscosity of the hydrocarbons and improving their ability to flow through the formation. The pressure of the water injection aids in driving the hydrocarbons having the gas dissolved therein toward a production well. WAG and SWAG techniques also increase sweep efficiency and the amount of gas needed for a particular EOR operation.
To further increase the sweep efficiency of a flooding composition, a surfactant may be included in the composition. The surfactant may reduce the interfacial tension between oil and water, thus decreasing capillary pressure. The surfactant may also alter rock wettability, making the formation water-wet or mixed-wet. Such interfacial tension reduction and/or altering of rock wettability may increase the recovery of hydrocarbons from the formation. Common EOR surfactants are non-volatile. Traditional surfactants for use in EOR operations have included dodecylbenzene sulfonic acid and its salts (having a lowest value boiling point of 290° C. (554° F.)), ethoxylates including ethylene oxide/propylene oxide block copolymers (having such high molecular weights that they decompose rather than have a normal boiling point on heating), and sulfonates. None of these traditional surfactants exhibit significant (and in some cases no) volatility under common downhole conditions.